Right, I've heard it theorized on other sites (TrekCore, for example) that DS9 and VOY will be released in HD, but the concern is whether they're worth the complete remastering that we got for TOS and TNG, or if they'll see something more like ENT where they upscale the existing masters (the difference being DS9/VOY will be more noticeably up-scaled than ENT).
The scenarios I've seen floating around are
1) Complete remastering - going back to the film negatives and reconstructing special effects ala TNG.
2) Use the existing masters and upscale them, ala ENT, which will result in something like "Trials and Tribble-ations" on TOS-R S3, which is noticeably lacking.
3) A combination, where they reconstruct the from the film negatives, but simply upscale effects sequences.
I think we'd all like to see option 1, and my guess is that's what CBS will do given, but in the end it'll all come down the money.
I think they'll go with option 1 at first. DS9 starts off with exactly the same setup as TNG - all ships models, only very limited CGI in total - so they can just proceed directly onward, which will be quicker and simpler (and thus cheaper!) than pausing to consider.
After that, there's two inflection points that could go either way - first, the sales figures for DS9 S1 and second, the point at which CGI starts to become a major part of the series. If sales come in far enough under target, they'll stop. And the CGI scenes are going to be more expensive to redo properly* - if there's a point at which upscaling comes into the picture, that'll be it.
*Yes, there was that bit a while back about *some* of the assets still surviving. But even if everything the guy saved is usable in HD with a simple rerender, as he claimed, that was the effects house that did more VOY than DS9.